Locked out of TV

Question

My toddler pressed something on the remote and the TV has locked us out. All that displays is a blue screen with a red padlock image in the top left hand corner. No buttons on the remote control or television set will work now except the on/off switch. We tried pressing every button on the remote and tried turning the power off at the main for a couple of hours to reset the TV but it still will only show the lock.